[Meta] Improve support for custom embeddable configurations at the dashboard panel level

[stacey-gammon]

We currently have limited support for overriding embeddable configuration settings at the dashboard panel level. For example, visualization colors and saved search column and sort settings.

But this support is lacking in many ways as well:

• No visible indication that any setting is being overridden
• No way to reset the overridden settings aside from removing and re-adding the panel.
• No way to expose these configuration setting with a panel action so they are easily edited.

A general way for embeddables to register or expose overridable variables would be very useful and cover a lot of edge cases. We can offer first class support in dashboard for some global configurations useful for all (or at least most) embeddables:

• Per panel filters
• Per panel time ranges
• Saved search used

But it would also be useful to come up with more first class support for other overridable variables and configuration. The embeddable can do whatever it likes with the variables internally, and dashboard can expose controls for the user to set or reset them.

This might also help us come up with a better solution for dashboard level index patterns, if the embeddable exposes a variable indexPatternId (or multiple indexPatternId variables to handle the case where an embeddable is using more than one index pattern).

Related:

• Custom time range interval at the dashboard level: Temporarily define interval in Dashboard for visualizations with Auto Intervals #7436

[stalaiya]

+1 for the Custom time range interval at the dashboard level: #7436

[ThomThomson]

Closing this in favour of #134706 because this functionality will be better covered by embeddable variables and controls which can change them.